The present invention relates to improved method and device for carrying out loggings in an activated nonflowing production well which provides improved measurements.
Various embodiments of a production log method and device for a nonflowing well requiring, for its bringing in, the implementing of activation means and notably for deflected wells, are described in French patent applications FR 2,637,939 and 89/04,225. This method and this device are particularly suitable for wells intended for producing oil containing effluents. It allows determination of the most favourable well portions notably when the wells pass through heterogeneous reservoirs producing oil, but also water and gas. The equipment of a well generally comprises a casing that is kept in position through cementing. A liner perforated on at least part of its length, which is an extension of the casing, is arranged in the total zone intended for the production. This liner can be possibly cemented, the cemented annular space being fitted with passageways linking the production zone to the liner. A flow string consisting of connected successive sections and fitted with centering elements is taken down into the liner. Sealing means are arranged in the annular space between the string and the liner in order to canalize in the string the total effluents produced by the production zone. The well being nonflowing, activation means are associated with the string and taken down into the well to suck up the effluents. These activation means comprise a pump which is driven by an electric or hydraulic motor.
The logging device comprises at least one set of measuring instruments arranged at the base of the flow string in order to measure the features of part of the flows sucked up by the pump. Sealing means are arranged around the string in order to separate in two parts the pipe or liner and to limit the measurements carried out to the effluents coming from only one of these two parts. The device may also comprise two measuring sets to measure separately the features of the flows coming from the two opposite parts of the pipe and homogenization means to mix up the effluents in case of a polyphase production, in order to improve the preciseness of the measurements carried out on the flows. By lengthening or shortening the string, the logging device is displaced in order to perform measurements on the effluents flowing out of the formation in various places of the well towards the inlet of the pump.
One problem still remains which distorts the measurements on the features of the flows. It is the more or less considerable pressure drop caused by each set of measuring instruments located in the flows flowing from the activated production zone, which has the effect of acting upon the flow rates measured in each place of the producing zone. According to whether the effluents come from upstream or downstream of said set, the flowing pressures are different. Besides, because of these pressure drops, an ill-defined part of the effluents tends to bypass the measuring instruments in case of a non cemented liner, and the resulting leak rates are not measured. It is therefore advisable to be able to correct this pressure drop so that the flow rates measured all along the pipe correspond to a substantially constant flowing pressure.